What is the Origin of Lipid Solubility?

The term is fundamental to physical chemistry and is applied directly to biological systems, particularly in pharmacokinetics and drug metabolism. It is often quantified by the partition coefficient, typically expressed as log P, which measures the ratio of a substance's concentration in a lipid phase versus an aqueous phase. The concept underpins the bioavailability and tissue distribution of lipophilic compounds.

What is the Mechanism of Lipid Solubility?

Highly lipid-soluble hormones, like testosterone and estrogen, can passively diffuse across the phospholipid bilayer of the cell membrane without the need for specific transporters. Once inside the cell, they can bind to intracellular receptors, such as nuclear receptors, to modulate gene expression, initiating the slower, genomic pathway. This direct access to the cell's interior and the central nervous system is a defining feature of steroid hormone action and their therapeutic efficacy.

Lipid Solubility ∞ Area

Lipid Solubility

Meaning

Lipid Solubility, also known as lipophilicity, is a physicochemical property describing the ability of a chemical compound, such as a hormone or drug, to dissolve in fats, oils, lipids, and non-polar solvents. This characteristic is critically important in endocrinology and pharmacology because it dictates a substance’s capacity to traverse the lipid-rich cell membranes and the blood-brain barrier. High lipid solubility is essential for steroid hormones to exert their genomic and non-genomic effects within target cells.